This invention relates to an electric musical instrument and, more particularly, to an electric bowed stringed musical instrument equipped with a plurality of mechanical vibration-to-electric signal converters.
Electric bowed stringed musical instruments are new members of the violin family. Strings are stretched over bodies, and the players bow the strings as similar to the members of the violin family, i.e., violins, violas and cellos. The players give rise to vibrations of the strings through the bowing, and the vibrating strings generate tones. Although the acoustic members of the violin family have respective resonators for increasing the loudness of the tones, the electric bowed stringed musical instruments do not have the resonators, but are equipped with pickup units. The pickup units convert the vibrations of the strings to electric signals representative of the waveforms of the mechanical vibrations, and the electric signals are amplified before conversion to electric tones through speaker systems. Thus, the electric bowed stringed musical instruments electrically increase the tones, and the resonators are not required for the electric bowed stringed musical instruments.
There is a compromise between the acoustic bowed stringed musical instrument and the electric bowed stringed musical instrument. An acoustic bowed stringed musical instrument is equipped with a pickup unit, and the pickup unit converts the vibrations of strings to an electric signal. The compromise is hereinbelow referred to as xe2x80x9celectric acoustic bowed stringed musical instrumentxe2x80x9d.
One of the attractive features of the electric bowed musical instrument is the silent mode. The resonators are indispensable for the acoustic bowed stringed musical instruments, and always increase the loudness through the resonation. It is not easy to deactivate the resonators. This means that players disturb the neighborhood. However, the resonators are eliminated from the electric bowed stringed musical instruments. The loudness is electrically increased. If the user connects a headphone to the amplifier, he or she can practice the bowing without disturbance of the neighborhood.
FIG. 1 shows a typical example of the electric violin. The electric violin 1 comprises a trunk 2, a frame body 3, a fingerboard 4, a peg box 5 and a chin rest 6. The frame body 3 has a contour like a half of the outline of the resonator, and sideward projects from the trunk 2. The chin rest 6 sideward projects from the rear portion of the trunk 2, and a player puts his or her chin on the chin rest 6 during the bowing. The fingerboard 4 projects from the front end of the trunk 2, and the peg box 5 is fixed to the leading end of the fingerboard 4.
The electric violin 1 further comprises four strings 7, peg screws 8, a tailpiece 9, a bridge 10 and a pickup unit 11. The peg screws 8 are turnably supported by the peg box 5, and the tailpiece is fixed to the upper surface of the rear portion of the trunk 2. The strings 7 are anchored to the tailpiece 9, and are wound up at the other end portions around the peg screws 8. The bridge 10 is provided on the upper surface of the trunk 2, and exerts tension to the strings 7. Although the component part 10 is not same as the bridge of the acoustic violin, the component part 10 is referred to as xe2x80x9cbridgexe2x80x9d in the description. The pickup unit 11 is provided between the upper surface of the trunk 2 and the lower surface of the bridge 10, and converts the vibrations to an electric signal.
FIG. 2 illustrates the bridge 10 and pickup unit 11 on the trunk 2. The bridge 10 is formed from a thin plate, and has a gently curved upper surface. Notches 10a are formed in the bridge 10, and are open to the outside on the gently curved upper surface. The strings 7 are received in the notches 10a so that the bridge 10 keeps the strings 7 spaced at intervals. While a player is bowing the strings 7, the strings 7 vibrate, and the vibrating strings 7 gives rise to vibrations of the bridge 10.
The bridge 10 has leg portions 10b and 10c, and piezoelectric transducers 11a and 11b are sandwiched between the lower surfaces of the leg portions 10b/10c and the upper surface of the trunk 2. The piezoelectric transducers 11a/11b convert the vibrations of the leg portions 10b/10c to the electric signal.
The electric signal is amplified, and the amplified electric signal passes through a filter circuit for producing an analog tone signal. The analog tone signal is supplied to a speaker system. However, if the analog tone signal is directly supplied to the speaker system, the audience feels the tones flat. This is because of the fact that the prior art electric violin does not have any resonator. The vibrations of the leg portions 10b/10c do not contain any reverb produced by the resonator. In order to impart the reverb to the tones, the amplified electric signal is supplied to a digital signal processor in another prior art system. The digital signal processor processes the electric signal for imparting the reverberation components to the electric signal, and, thereafter, the electric signal is supplied from the digital signal processor to the speaker system.
The first problem inherent in the prior art electric violin is poor promptitude in following up the bowing. In detail, the piezoelectric transducers 11a/11b are liable to respond to the transverse vibrations indicated by arrow AR1. While the strings 7 are vibrating through the bowing, the transverse vibration components give rise to rocking motion of the bridge 10 as indicated by arrows AR2 and AR3 and vice versa. The piezoelectric transducers 11a/11b are arranged in such a manner as to be oppositely polarized. In this situation, when the leg portions 10b/10c are moved in the directions of arrows AR2/AR3, the piezoelectric transducers 11a/11b are polarized as shown in FIG. 3, and a large amount of electric charges flow.
The arrangement of piezoelectric transducers 11a/11b is less desirable for the vertical vibration components. If the strings 7 vertically vibrate as indicated by arrow AR4 (see FIG. 4), the leg portions 10b/10c vibrate in the same direction as indicated by arrows AR5 and vice versa, and the piezoelectric transducers 11a/11b are oppositely polarized. Most of the electric charges in one piezoelectric transducer 11a/11b are canceled with the electric charges in the other piezoelectric transducer 11b/11a, and only a negligible amount current flows. Thus, the piezoelectric transducers 11a/11b hardly convert the vertical vibration components to the electric signal.
However, the bowing is not always reflected on the transverse vibrations. Although the transverse vibration components are the major factor of certain sorts of bowing, other sorts of bowing is influential in the vertical vibration components. This means that the prior art electric violin can not promptly respond to the other sorts of bowing. This is the first problem inherent in the prior art electric violin.
The second problem is poor fidelity of the tones. The piezoelectric transducers 11a/11b are corresponding to condensers in an equivalent circuit, and have strong influence on the output impedance of the pickup unit 11. If the condensers, i.e., the piezoelectric transducers have large capacitance, the out-put impedance becomes small, and the cut-off frequency is low. On the other hand, when the capacitance is small, the output impedance is large, and the cut-off frequency is high. This means that the electric signal does not contain the low frequency components. In other words, the electric tones generated from the electric signal are different from the acoustic tones produced by a corresponding acoustic bowed stringed instrument. Another drawback due to the large output impedance is a large amount of noise. The thinner the piezoelectric elements, the larger the capacitance. However, the thin piezoelectric transducers are expensive. Relatively thick piezoelectric transducers are employed in the actual prior art bowed stringed musical instruments from the viewpoint of the production cost, and this results in the poor fidelity.
The third problem is inherent in the prior art bowed stringed musical instrument of the type producing an electric tone on the basis of the plural electric signals generated by the plural vibration detectors. Although the digital signal processor can impart the reverb to the electric tones, it is impossible to express the difference in the position of sound image due to change of string bowed by the player. For example, the audience can discriminate the acoustic tones generated at a position far from them from the acoustic tones generated at another position close to them. However, even when a player changes the bowed string of the prior art bowed stringed musical instrument from one to another, the player can not discriminate the presently bowed string from the previously bowed string. In other words, the player can not notice the movement of the image through the electric tones. This is the third problem.
The problems are also encountered in other sorts of electric bowed stringed musical instruments, and are inherent to the electric bowed stringed musical instruments.
It is therefore an important object of the present invention to provide an electric bowed stringed musical instrument, which produces electric tones clear in pitch and close in timbre to acoustic tones.
It is also an important object of the present invention to provide an electric bowed stringed musical instrument, which produces electric tones clear in pitch without sacrifice of production cost.
It is another important object of the present invention to provide an electric bowed stringed musical instrument, which produces electric tones expressing change of bowed strings.
In accordance with one aspect of the present invention, there is provided an electric bowed stringed musical instrument for generating electric tones comprising a vibratory body, at least one string stretched over the vibratory body, and bowed for generating vibrations, the vibrations being propagated from the aforesaid at least one string to the vibratory body, a pickup unit connected to the vibratory body and having a first detector for converting transverse vibration components of the vibrations to a first electric signal and a second detector for converting vertical vibration components of the vibrations to a second electric signal, and a signal processing system connected to the pickup unit and including a first filter for transmitting low-frequency signal components of the first electric signal, a second filter for transmitting high-frequency signal components of the second electric signal and a signal producer connected to the first and second filters for producing a tone signal from the low-frequency signal components and the high-frequency signal components.
In accordance with another aspect of the present invention, there is provided an electric bowed stringed musical instrument for generating electric tones comprising a vibratory body, at least one string stretched over the vibratory body and bowed for generating vibrations, the vibrations being propagated from the aforesaid at least one string to the vibratory body, a pickup unit connected to the vibratory body and including plural vibration-to-electric signal converters having respective parasitic capacitances and connected in parallel to a constant potential source for converting the vibrations to an electric signal, and a signal processing system connected to the plural vibration-to-electric signal converters, and producing a tone signal from the electric signal.
In accordance with yet another aspect of the present invention, there is provided an electric bowed stringed musical instrument for generating electric tones comprising a vibratory body, plural strings stretched over the vibratory body and selectively bowed for generating vibrations, the vibrations being propagated from the plural strings to the vibratory body, a pickup unit connected to the vibratory body and including plural vibration-to-electric signal converters each different in distance to the plural strings, the vibratory body decaying the vibrations propagated from the bowed string or strings to the plural vibration-to-electric signal converters depending upon the distances between the bowed string or strings and the plural vibration-to-electric signal converters so that the vibration-to-electric signal converters generates electric signals differently influenced by the bowed string or strings, and a signal processing system connected to the plural vibration-to-electric signal converters, and separately producing tone signals from the electric signals.